Add default_colors API to Theme DSL for setting terminal fg/bg

lib/textbringer/commands/windows.rb

@@ -84,6 +84,20 @@ module Commands
       end
     end
 
+    define_command(:set_foreground_color, doc: <<~EOD) do
+        Set the default foreground color.
+      EOD
+      |color = read_from_minibuffer("Foreground color: ")|
+      Window.set_default_colors(color, nil)
+    end
+
+    define_command(:set_background_color, doc: <<~EOD) do
+        Set the default background color.
+      EOD
+      |color = read_from_minibuffer("Background color: ")|
+      Window.set_default_colors(nil, color)
+    end
+
     define_command(:list_buffers, doc: <<~EOD) do |buffers = Buffer.list|
         List the existing buffers.
       EOD

lib/textbringer/theme.rb

@@ -73,6 +73,7 @@ def initialize(name)
       @name = name
       @palettes = {}
       @face_definitions = []
+      @default_colors = nil
     end
 
     attr_reader :name
@@ -87,6 +88,10 @@ def face(name, **attrs)
       @face_definitions << [name, attrs]
     end
 
+    def default_colors(foreground:, background:)
+      @default_colors = { foreground: foreground, background: background }
+    end
+
     def activate
       mode = self.class.background_mode
       tier = self.class.color_tier
@@ -113,6 +118,33 @@ def activate
         Face.define(face_name, **resolved)
       end
       @@current = self
+      apply_default_colors(palette, tier)
+    end
+
+    private
+
+    def apply_default_colors(palette, tier)
+      if @default_colors
+        fg = resolve_default_color(@default_colors[:foreground], palette, tier)
+        bg = resolve_default_color(@default_colors[:background], palette, tier)
+      else
+        fg = "default"
+        bg = "default"
+      end
+      Window.set_default_colors(fg, bg)
+    end
+
+    def resolve_default_color(val, palette, tier)
+      if val.is_a?(Symbol)
+        color = palette.resolve(val, tier)
+        unless color
+          raise EditorError,
+                "Unknown palette color :#{val} for default_colors"
+        end
+        color
+      else
+        val || "default"
+      end
     end
 
     private_class_method def self.detect_background_via_osc11

lib/textbringer/themes/catppuccin.rb

@@ -68,6 +68,8 @@
     p.color :rosewater, hex: "#d78787", ansi: "red"
   end
 
+  t.default_colors foreground: :text, background: :base
+
   # Programming faces (from catppuccin/nvim syntax.lua)
   t.face :comment,                foreground: :overlay2
   t.face :preprocessing_directive, foreground: :pink

lib/textbringer/themes/github.rb

@@ -48,6 +48,8 @@
     p.color :darkblue, hex: "#c1daec", ansi: "blue"         # dcolors.darkblue = blue1
   end
 
+  t.default_colors foreground: :fg, background: :bg
+
   # Programming faces
   t.face :comment,                  foreground: :comment   # Comment = base2
   t.face :preprocessing_directive,  foreground: :red       # PreProc = red

lib/textbringer/themes/gruvbox.rb

@@ -47,6 +47,8 @@
     p.color :orange, hex: "#d75f00", ansi: "red"
   end
 
+  t.default_colors foreground: :fg1, background: :bg0
+
   # Programming faces
   t.face :comment,                foreground: :gray
   t.face :preprocessing_directive, foreground: :aqua

lib/textbringer/themes/molokai.rb

@@ -27,6 +27,8 @@
     p.color :search,  hex: "#ffd787", ansi: "yellow"       # 222  Search bg
   end
 
+  t.default_colors foreground: :fg, background: :bg
+
   # Programming faces
   t.face :comment,                  foreground: :comment
   t.face :preprocessing_directive,  foreground: :green

lib/textbringer/themes/sonokai.rb

@@ -26,6 +26,8 @@
     p.color :purple,   hex: "#d787d7", ansi: "magenta"
   end
 
+  t.default_colors foreground: :fg, background: :bg0
+
   # Programming faces (from sonokai highlight groups)
   t.face :comment,                foreground: :grey
   t.face :preprocessing_directive, foreground: :red

lib/textbringer/themes/tokyonight.rb

@@ -29,6 +29,8 @@
     p.color :blue5,   hex: "#89ddff", ansi: "cyan"         # Operator, punctuation delimiters
   end
 
+  t.default_colors foreground: :fg, background: :bg
+
   # Programming faces
   t.face :comment,                  foreground: :comment
   t.face :preprocessing_directive,  foreground: :cyan     # PreProc = c.cyan

lib/textbringer/window.rb

@@ -33,6 +33,8 @@ class Window
     @@minibuffer_selected = nil
     @@echo_area = nil
     @@has_colors = false
+    @@default_fg = "default"
+    @@default_bg = "default"
 
     def self.list(include_echo_area: false)
       if include_echo_area
@@ -133,8 +135,13 @@ def self.colors
     end
 
     def self.set_default_colors(fg, bg)
-      Curses.assume_default_colors(Color[fg], Color[bg])
-      Window.redraw
+      new_fg = fg || @@default_fg
+      new_bg = bg || @@default_bg
+      Curses.assume_default_colors(Color[new_fg], Color[new_bg])
+      @@default_fg = new_fg
+      @@default_bg = new_bg
+      Face.define(:default, foreground: new_fg, background: new_bg)
+      Window.redraw if @@started
     end
 
     def self.load_faces
@@ -708,7 +715,8 @@ def redisplay_mode_line
       @mode_line.addstr(" #{line},#{column}")
       @mode_line.addstr(" (#{@buffer.mode_names.join(' ')})")
       @mode_line.addstr(" " * (columns - @mode_line.curx))
-      @mode_line.attr_set(0, 0)
+      default = Face[:default]
+      @mode_line.attr_set(default&.text_attrs || 0, default&.color_pair || 0)
       @mode_line.noutrefresh
     end
 
@@ -948,6 +956,7 @@ def get_char
     end
 
     def apply_face_attrs(win, face)
+      face ||= Face[:default]
       win.attr_set(face&.text_attrs || 0, face&.color_pair || 0)
     end
 
@@ -967,7 +976,8 @@ def apply_window_attrs(win)
         end
         win.attr_set(text_attrs, face.color_pair)
       else
-        win.attr_set(0, 0)
+        default = Face[:default]
+        win.attr_set(default&.text_attrs || 0, default&.color_pair || 0)
       end
     end
   end
@@ -1016,7 +1026,8 @@ def redisplay
           @window.addstr(@buffer.input_method_status)
         end
         @window.setpos(0, 0)
-        @window.attr_set(0, 0)
+        default = Face[:default]
+        @window.attr_set(default&.text_attrs || 0, default&.color_pair || 0)
         @in_region = false
         @in_isearch = false
         @current_hl_face = nil

test/textbringer/test_theme.rb

@@ -106,6 +106,60 @@ def test_activate_with_inherit
     Face.delete(:derived_kw)
   end
 
+  def test_activate_sets_default_colors
+    Theme.define "test_defcol" do |t|
+      t.palette :dark do |p|
+        p.color :fg, hex: "#ffffff", ansi: "white"
+        p.color :bg, hex: "#000000", ansi: "black"
+      end
+      t.default_colors foreground: :fg, background: :bg
+      t.face :test_defcol_face, foreground: :fg
+    end
+    Theme["test_defcol"].activate
+    fg_num = Color["#ffffff"]
+    bg_num = Color["#000000"]
+    assert_equal([fg_num, bg_num], Curses.default_colors)
+  ensure
+    Face.delete(:test_defcol_face)
+  end
+
+  def test_activate_resets_default_colors_when_not_specified
+    Theme.define "test_with_defcol" do |t|
+      t.palette :dark do |p|
+        p.color :fg, hex: "#ffffff", ansi: "white"
+        p.color :bg, hex: "#000000", ansi: "black"
+      end
+      t.default_colors foreground: :fg, background: :bg
+      t.face :test_wdc_face, foreground: :fg
+    end
+    Theme["test_with_defcol"].activate
+    assert_not_equal([-1, -1], Curses.default_colors)
+
+    Theme.define "test_no_defcol" do |t|
+      t.palette :dark do |p|
+        p.color :fg, hex: "#ffffff", ansi: "white"
+      end
+      t.face :test_ndc_face, foreground: :fg
+    end
+    Theme["test_no_defcol"].activate
+    assert_equal([-1, -1], Curses.default_colors)
+  ensure
+    Face.delete(:test_wdc_face)
+    Face.delete(:test_ndc_face)
+  end
+
+  def test_activate_default_colors_raises_on_unknown_palette
+    Theme.define "test_bad_defcol" do |t|
+      t.palette :dark do |p|
+        p.color :fg, hex: "#ffffff", ansi: "white"
+      end
+      t.default_colors foreground: :nonexistent, background: :fg
+    end
+    assert_raise(EditorError) do
+      Theme["test_bad_defcol"].activate
+    end
+  end
+
   def test_load_default_activates_faces
     face = Face[:comment]
     assert_not_nil(face)

test/textbringer/test_window.rb

@@ -432,6 +432,34 @@ def test_s_set_default_colors
     assert_equal([-1, -1], Curses.default_colors)
   end
 
+  def test_s_set_default_colors_partial_update
+    red = Color["red"]
+    blue = Color["blue"]
+    green = Color["green"]
+    Window.set_default_colors("red", "blue")
+    assert_equal([red, blue], Curses.default_colors)
+
+    # Update only bg, fg should be preserved
+    Window.set_default_colors(nil, "default")
+    assert_equal([red, -1], Curses.default_colors)
+
+    # Update only fg, bg should be preserved
+    Window.set_default_colors("green", nil)
+    assert_equal([green, -1], Curses.default_colors)
+  end
+
+  def test_s_set_default_colors_empty_string_ignored
+    red = Color["red"]
+    blue = Color["blue"]
+    Window.set_default_colors("red", "blue")
+    assert_equal([red, blue], Curses.default_colors)
+
+    # Empty string should be treated as error
+    assert_raise(EditorError) do
+      Window.set_default_colors("", "")
+    end
+  end
+
   private
 
   def window_string(window)